The study assessed the differences in electromyographic (EMG) activity recorded during clenching in women with chronic unilateral temporomandibular disorders (TMDs) as compared to control subjects. Seventy-five full dentate, normo-occlusion, right-handed, similarly aged female subjects were recruited. Twenty five subjects presented with right side TMD, 25 presented with left side TMD and 25 pain-free control subjects participated. Using integrated surface EMG over a 1 s contraction, the anterior temporalis and masseter muscles were evaluated bilaterally while subjects performed maximum voluntary clenching. Lower EMG activation was observed in patients with TMD as compared to control subjects (temporalis: 195.74+/-18.57 vs. 275.74+/-22.11, P=0.011; masseters: 151.09+/-17.37 vs. 283.29+/-31.87, P<0.001). An asymmetry index (SAI) was calculated to determine ratios of right to left sided activation. Patients with right-sided TMD demonstrated preferential use of their left-sided muscles (SAI -5.35+/-4.02) whereas patients with left-sided TMD demonstrated preferential use of their right-sided muscles (SAI 6.95+/-2.82), (P=0.016). This unilateral reduction in temporalis and masseter activity could be considered as a specific protective functional adaptation of the neuromuscular system due to nociceptive input. The asymmetry index (SAI) may be a useful measure in discriminating patients with right vs. left-sided TMD.

Evaluation of masticatory muscle activanterior digastric muscle (3·49 mV) on the left side. Overall mean activity during clenching was 66·77 9 ity by surface electromyography (EMG) is a valuable tool for diagnosing dysfunction of the masticatory 35·22 mV, which is about half that observed in healthy subjects (110·30 9 82·97 mV). During leftapparatus. However, controversy exists with regard ward movement of the jaw, activity was on average to the usefulness of the EMG for patients with highest in the left digastric, while during rightward temporomandibular disorders (TMD). Forty patients with TMD were subjected to surface EMG of movement, activity was on average highest in the right anterior temporal (AT). Our results thus indithe masticatory muscles. These patients had concate that patients with temporomandibular joint sulted because of temporomandibular pain and (TMJ) disorder show: (1) a slight increase in basal clicks. In most cases (75%), the symptoms affected tone;(2) a significantly reduced capacity for clenchthe patient's left side. Overall mean resting activity was 2·52 mV91·25 mV (s.d.), which is slightly higher ing; and (3) an apparently paradoxical inhibition of than in comparable healthy subjects (1·92 9 the dysfunctional-side AT during movement of the 1·20 mV). Mean resting activity was highest in the mandible towards that side.

Evaluation of masticatory muscle activity by surface electromyography (EMG) is a valuable tool for diagnosing dysfunction of the masticatory apparatus. However, controversy exists with regard to the usefulness of the EMG for patients with temporomandibular disorders (TMD). Forty patients with TMD were subjected to surface EMG of the masticatory muscles. These patients had consulted because of temporomandibular pain and clicks. In most cases (75%), the symptoms affected the patient's left side. Overall mean resting activity was 2.52 microV+/-1.25 microV (s.d.), which is slightly higher than in comparable healthy subjects (1.92+/-1.20 microV). Mean resting activity was highest in the anterior digastric muscle (3.49 microV) on the left side. Overall mean activity during clenching was 66.77+/-35.22 microV, which is about half that observed in healthy subjects (110.30+/-82.97 microV). During leftward movement of the jaw, activity was on average highest in the left digastric, while during rightward movement, activity was on average highest in the right anterior temporal (AT). Our results thus indicate that patients with temporomandibular joint (TMJ) disorder show: (1) a slight increase in basal tone; (2) a significantly reduced capacity for clenching; and (3) an apparently paradoxical inhibition of the dysfunctional-side AT during movement of the mandible towards that side.

Sleep bruxism (SB) and obstructive sleep apnoea syndrome (OSAS) share common pathophysiologic pathways. We aimed to study the presence and relationship of SB in a OSAS population. Patients referred with OSAS suspicion and concomitant SB complains were evaluated using a specific questionnaire, orofacial evaluation and cardio-respiratory polygraphy that could also monitor audio and EMG of the masseter muscles. From 11 patients studied 9 had OSAS. 55.6% were male, mean age was 46.3±11.3 years, and apnea hypopnea index of 11.1±5.7/h. Through specific questionnaire 55.6% had SB criteria. Orofacial examination (only feasible in 3) confirmed tooth wear in all. 77.8% had polygraphic SB criteria (SB index>2/h). Mean SB index was 5.12±3.6/h, phasic events predominated (72.7%). Concerning tooth grinding episodes, we found a mean of 10.7±9.2 per night. All OSAS patients except two (77.8%) had more than two audible tooth-grinding episodes. These two patients were the ones with the lowest SB index (1.0 and 1.4 per hour). Only in one patient could we not detect tooth grinding episodes. There was a statistically significant positive correlation between tooth grinding episodes and SB index and phasic event index (R=0.755, p=0.019 and R=0.737, p=0.023 respectively, Pearson correlation). Mean apnoea to bruxism index was 0.4/h, meaning that only a minority of SB events were not secondary to OSAS. We could not find any significant correlation between AHI and bruxism index or phasic bruxism index (R=-0.632 and R=-0.611, p>0.05, Pearson correlation). This pilot study shows that SB is a very common phenomenon in a group of mild OSAS patients, probably being secondary to it in the majority of cases. The new portable device used may add diagnostic accuracy and help to tailor therapy in this setting.

Wearing an intraoral jaw-protruding splint could enhance respiratory function in clinical settings and eventually exercise performance. Purpose: The authors studied the acute effect of wearing a lower-jaw-forwarding splint at different protruding percentages (30% and 50%) across a wide range of running exercise intensities. Methods: A case study was undertaken with a highly trained and experienced 27-year-old female triathlete. She performed the same incremental intermittent treadmill running protocol on 3 occasions wearing 3 different intraoral devices (30% and 50% maximum range and a control device) to assess running physiological and kinematic variables. Results: Both the 30% and 50% protruding splints decreased oxygen uptake and carbon dioxide production (by 4%–12% and 1%–10%, respectively) and increased ventilation and respiratory frequency (by 7%–12% and 5%–16%, respectively) along the studied running intensities. Exercise energy expenditure (approximately 1%–14%) and cost (7.8, 7.4, and 8.0 J·kg−1·m−1 for 30%, 50%, and placebo devices, respectively) were also decreased when using the jaw-protruding splints. The triathlete’s lower limbs’ running pattern changed by wearing the forwarding splints, decreasing the contact time and stride length by approximately 4% and increasing the stride rate by approximately 4%. Conclusions: Wearing a jaw-protruding splint can have a positive biophysical effect on running-performance-related parameters.